Publication Date
2023
Document Type
Dissertation/Thesis
First Advisor
Stansell, Nathan D.
Degree Name
Ph.D. (Doctor of Philosophy)
Legacy Department
Department of the Earth, Atmosphere and Environment (EAE)
Abstract
Terrestrial records of hydroclimate variability from Central and South America were developed to better constrain previously unknown regional responses to a range of hydroclimate drivers in the recent past. Developing these late Holocene terrestrial hydroclimate records improves our understanding of past hydroclimate variability by increasing temporal resolution and allows us to further understand complexities in spatial dynamics of the climate system. From South-Central Chile, a geomorphic analysis of landforms emplaced in a glacial valley indicated a positive glacial mass balance in the recent past. A high-precision chlorine-36 chronology was developed from basaltic boulders, with additional minimum constraining ages from Araucaria araucana trees to determine the timing of moraine emplacement in the valley. We then used a coupled glacial mass balance and flow model to add quantitative constraints to various regional hydroclimate parameters (i.e., temperature, precipitation, etc.) that would result in glacial expansion to the mapped moraine locations during peak Neoglaciation. Lacustrine records of hydroclimate variability from Lake Chichój, located in the central highland of Guatemala, were also developed. Composed of three subbasins, the steep-sided morphology of the western subbasin has resulted in a tendency for both earthquakes and floods to induce depositional events. A high-resolution geochemical, geophysical, and sedimentological analysis of sediment cores from the western basin reveal instances of extreme flooding of the catchment, as well as an enhanced assessment of regional fault ruptures preserved as soft sediment deformation structures. A total of n=15 earthquakes with magnitudes greater than 7 were identified throughout the record, including the 1976 C.E. rupture of the Motagua Fault and the 1816, 1785 and 1538 C.E. ruptures of the Polochic Fault. A second core taken from the sill between subbasins was further developed for an oxygen isotope-based record of hydroclimate variability. Here, it was determined that Lake Chichój was hydrologically closed from the beginning of the record at ~720 C.E. until ~1550 C.E., when a transition occurred to a more hydrologically open system. Furthermore, the developed isotopic records suggest that the central highlands experienced a wetter Little Ice Age, expressed as lower isotopic values than those during the interval spanning the Medieval Climate Anomaly, providing valuable information about precipitation and evaporation dynamics in the central highlands of Guatemala over the latest Holocene.Collectively, these data are used to quantify the magnitude and timing of changes in rainfall patterns, useful for identifying natural cycles of climate variability only perceivable in terrestrial records. As regional instrumental records of temperature and rainfall span less than 200-years, the sub-decadal resolution of these late Holocene records provide longer-term context to assess modern and future changes to regional hydroclimate. The development of these high-resolution paleoclimate records will further constrain our understanding of the response of tropical rainfall to a range of drivers, such as ocean-atmospheric influences during the recent past.
Recommended Citation
Price, Brittany N., "Late Holocene Terrestrial Hydroclimate Reconstructions from Central and South American Sites" (2023). Graduate Research Theses & Dissertations. 7844.
https://huskiecommons.lib.niu.edu/allgraduate-thesesdissertations/7844
Extent
197 pages
Language
en
Publisher
Northern Illinois University
Rights Statement
In Copyright
Rights Statement 2
NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.
Media Type
Text
